In general, graphene has recently gained interest as a filler for composite materials (e.g., because of its intrinsic mechanical, thermal, and electrical properties). For example, graphene's lack of solubility in substantially all solvents has led to the common practice of either using graphene oxide or reduced graphene oxide in the place of pristine graphene sheets. However, both graphene oxide and reduced graphene oxide have significantly reduced mechanical, thermal, and electrical properties when compared to the pristine graphene material.
As noted, graphene has been sought after for its use as a filler in composite materials (e.g., because of its outstanding electrical, thermal, and mechanical properties). Unlike metals with comparable properties, graphene has a relatively low density of about 2.2 g/cm3 and large theoretical surface area to mass ratio of around 2600 m2/g. Problems in dispersion have plagued the field and have unfortunately led to the use of both graphene oxide (GO) and reduced graphene oxide (RGO) in the place of pristine graphene sheets. Both of these substitutes, however, have greatly reduced properties when compared to the pristine material.
In GO, this is a result of the disruption of the delocalized electron network with the addition of oxygen functionalities. Reduction of the GO sheets to make RGO does remove most of the oxygen functionalities; however, it also leaves behind defects such as dislocated bonds that again disrupt the delocalized electron network found in pristine graphene and results in the reduction of the properties mentioned. The lower strength and conductivities are then passed on to the final composite. Some current methods utilizing GO and RGO have processing problems as well. Some processing problems include: harsh in-situ chemical reduction steps, as well difficult solvent removal in the solution mixing method; dispersion problems associated with the high viscosities of melted polymers, as well as the breaking and buckling of sheets from shear stress in the melt blending method; and dispersion and manipulation issues that arise from increases in viscosity in the in-situ polymerization method.
Thus, an interest exists for improved composite materials utilizing graphene as a filler, and related fabrication methods. These and other inefficiencies and opportunities for improvement are addressed and/or overcome by the systems, assemblies and methods of the present disclosure.